JP2926777B2 - Shape measuring device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a shape measuring apparatus, and observes interference fringes of a laser beam reflected on an object to be measured and focuses the image on the surface of the object while focusing the camera. The shape is measured accurately.

(Prior Art) FIG. 4 shows a conventional shape measuring apparatus.
1 is a laser device, 102 is a prism, 103 is a camera, 104 is PS
It is a shape measuring element like D.

The laser beam reflected by the object 105 is
The surface shape of the measured object 105 is measured by detecting the displacement from the focal point of the camera 103 by the shape measuring element 104.

(Problems to be Solved by the Invention) By the way, there is a limit in reducing the luminous flux of the laser light emitted from the laser device 101 (generally, the limit is to reduce the diameter to about Φ = 100 microns). Is flat, the distribution of the laser beam incident on the shape measuring element 104 becomes a Gaussian distribution as shown by a solid line M in FIG. 5, and the surface position of the object 105 to be measured is determined from the voltages VA and VB generated by the light flux. calculate.

However, for example, fine irregularities e
When a part of the light beam of the laser beam is strongly specularly reflected on the unevenness e and the reflected light K enters the shape measuring element 104, the distribution of the incident light becomes a deviation distribution indicated by a broken line N,
A measurement error will occur.

Therefore, an object of the present invention is to provide a measuring means capable of accurately measuring the shape of an object having minute unevenness.

(Means for Solving the Problems) The present invention provides a laser device, an optical element that reflects laser light emitted from the laser device toward an object to be measured, and a device to be measured that is obliquely above the object to be measured. The laser light reflected obliquely upward to the surface of the object is directly incident on the optical element without being transmitted through the optical element, and is detected, thereby detecting the shape of the object to be measured and the laser light reflected by the object to be measured. An optical unit integrally assembled with a camera for observing laser light, a distance adjusting device for the camera to an object to be measured, and the distance adjusting device operated based on image data of interference fringes sent from the camera. A control device for causing the optical element to provide an optical path length difference to the laser light irradiated on the object to be observed by the camera for observing interference fringes. Transparent plate with And the laser device irradiates the laser light from the side toward the transparent plate, and the laser light transmitted upward through the transparent plate is observed by the camera. A shape measuring apparatus characterized in that:

(Operation) In the above configuration, when a normal (flat) surface is irradiated with laser light, interference fringes observed by a camera are stored in advance in the control device as master interference fringes. Then, the object to be measured is irradiated with laser light, and while observing the interference fringes with the camera, the surface shape of the object to be measured is measured by the shape measuring element. When the interference fringes do not match the master interference fringe, The focus of the camera is adjusted by activating the distance adjustment device to coincide.

Example Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view of a shape measuring apparatus, in which A is an optical unit, and includes a camera 1 such as a CCD camera capable of observing a contrast of luminance, and a lens barrel 2 integrally assembled below the camera. Have. A semiconductor laser device 3 for irradiating a laser beam is housed in a side portion of the lens barrel 2.
At a position optically coaxial with the camera 1 and the laser device 3,
An optical element 4 is provided. In FIG. 2, this optical element 4 is provided on both front and back sides of a transparent plate 4a such as a glass plate.
It is formed by coating the reflection plates 4b and 4c. The thickness of the transparent plate 4a is, for example, about 0.5 mm. The reflecting surfaces 4b and 4c are half mirrors that reflect a part of the light and transmit a part of the light. As shown in FIG.
Is inclined at an angle of 45 °, and the laser device 3 irradiates the optical element 4 with laser light from the side. The laser light transmitted through the optical element 4 upward enters the camera 1 above.

Reference numeral 5 denotes a case integrally assembled to the lens barrel 2 by a bracket 6, in which a shape measuring element 7 such as a PSD is housed. Reference numerals 8 and 9 denote light-collecting elements.

In FIG. 1, reference numeral B denotes a distance adjusting device which raises and lowers the optical unit A to adjust the focal point of the camera 1, that is, the distance to the object to be measured. Slider 12 freely mounted
And a motor MZ. The camera 1 has a slider 12
When the motor MZ is driven, the optical unit A moves up and down to adjust the position of the camera 1.

C is an XY table provided below the optical unit A, which is composed of an X table 15, a Y table 16, and respective drive motors MX and MY, and a DUT set on the upper surface thereof. Move P in the XY direction. D is a control device such as a computer, and the camera 1, the shape measuring element 7, the motors MX, MY, MZ, etc. are connected to the control device D.

The laser light emitted from the laser device 3 is
Are reflected by the two reflecting surfaces 4b and 4c and are incident on the surface of the object to be measured p. A part of the laser light irregularly reflected on this surface is incident on the shape measuring element 7, and a part thereof is reflected upward. Then, the light passes through the optical element 4 and is observed by the camera 1. In this case, as shown in FIG.
The light is reflected obliquely upward on the surface of the optical element 4, and is directly incident on the shape memory element 7 without being transmitted through the optical element 4, and is detected. Here, since the optical element 4 has two reflecting surfaces 4b and 4c, the light reflected by the two reflecting surfaces 4b and 4c has an optical path length difference L based on the thickness of the optical element 4, and Due to this phase difference, an interference fringe as shown in FIG. 3 is observed in the camera 1, but as will be described later, this unit uses a camera based on the image data of the interference fringe sent from the camera 1. In order to adjust the focus, the distance adjusting device B is operated to move the optical unit A up and down.

This apparatus has the above configuration, and the measuring method will be described next.

Prior to measuring the shape of the object P, when a normal (flat) surface is irradiated with laser light, the interference fringes observed by the camera 1 are stored in the control device D as master interference fringes. This interference fringe is stored in the control device D as luminance level data.

Next, the object P set on the XY table C is irradiated with laser light, and while the interference fringes of the laser light reflected on the object P are observed by the camera 1, the laser light irregularly reflected on the object P is observed. Light is detected by the shape measuring element 7 and its surface shape is measured as a displacement from the focal point of the camera 1. When this interference fringe coincides with the master interference fringe, the focus of the camera 1 is normal and the shape measuring element 7
Is calculated by the control device D based on the output of.

If irregularities are present on the surface of the object P, the focus of the camera 1 will be out of order and a measurement error will occur. In this case, since the focus position has changed, the interference fringes observed by the camera 1 will be the master interference fringes. By driving the motor MZ to move up and down the optical unit A so that the interference fringe coincides with the master interference fringe, the camera 1 is focused and the output of the shape measuring element 7 is adjusted. Is read.

As described above, the present means reads the output of the shape measuring element 7 while observing the interference fringes and adjusting the focus of the camera 1, so that the shape of the object P can be measured very precisely. .

(Effects of the Invention) As described above, according to the present invention, the shape of the object to be measured can be accurately measured by focusing the camera while observing the interference fringes with the camera.

[Brief description of the drawings]

1 shows an embodiment of the present invention. FIG. 1 is a perspective view of a shape measuring device, FIG. 2 is a sectional view, FIG. 3 is a plan view of interference fringes, and FIG. FIG. 5 is a side view of the apparatus, and FIG. 5 is a side view of the shape measuring element. A: Optical unit B: Distance adjusting device D: Control device P: Object to be measured 1: Camera 3: Laser device 4: Optical element 7: Shape measuring element

Claims (1)

(57) [Claims] 1. A laser device, an optical element for reflecting laser light emitted from the laser device toward an object to be measured, and an oblique upper portion of the object to be measured and obliquely reflected on a surface of the object to be measured. A shape measuring element for measuring the shape of the object to be measured by directly entering the laser light without being transmitted through the optical element and detecting the laser light, and a camera for observing the laser light reflected on the object to be measured. An optical unit integrally assembled, a distance adjusting device for the camera to the object to be measured, and a control device for operating the distance adjusting device based on image data of interference fringes sent from the camera, The optical element is an optical element for providing an optical path length difference to the laser light irradiated on the object to be measured for observing interference fringes by the camera, and is formed of a transparent plate having reflection surfaces on both front and back surfaces. Oblique transparent plate A shape measuring apparatus characterized in that the laser device emits laser light from the side toward the transparent plate, and the laser light transmitted upward through the transparent plate is observed by the camera.